Fuel control for turbine driven compressor unit



I. E. SPEER FUEL CONTROL FOR TURBINE DRIVEN COMPRESSOR UNIT Original Filed Feb. 8; 1951 3 Sheets-Sheet 1 T N E V E R,

.E H P S O M T A INVENTOR.

IVAN E. .SPEER 7 KKK ATTORNEY I. E. SPEER May 19, 194

FUEL CONTROL FOR TURBINE DRIVEN COMPRESSOR UNIT 3 Sheets-Sheet 2 Original Filed Feb. 8, 1951 INVENTOR.

IVA/V E SPEER ATTORNEY May 19, 1964 LE. SPEER 3 FUEL CONTROL FOR TURBINE DRIVEN COMPRESSOR UNIT Original Filed Feb, 8', 1951. 5 Sheets-Sheet 3 2s 3 VALVE ACTUATING MECHANISM ENGINE STARTER PNEUMATIC SWITCH STARTING r l l l l l l l RELAY l l I 69 VERSPEED RELAY INVENTOR.

IVAN E. SPEER A TTORNE Y United States Patent 3,133,414 FUEL CONTROL FOR TURBINE DRIVEN COMPRESSOR UNIT Ivan E. Speer, Phoenix, Ariz., assignor to The Garrett Corporation, Los Angeles, Calif, a corporation of California Application Sept. 7, 1956, Ser. No. 608,555, now Patent No. 3,092,346, datedOct. 3,1961, which is a division of application Ser. No. 209,929, Feb. 8, 1951, now Patent No. 2,763,985, dated Sept. 25, 1956. Divided and this appiication June 19, 1961, Ser. No. 118,012

4 Claims. (Ci. 60-3914) The present invention relates generally to apparatus for supplying a fluid such as air to a point of use for power and other purposes. It is more particularly concerned with a packaged unit which may be utilized in aircraft. In this connection, the apparatus is especially adapted for supplying air to pneumatic starters for turbojet and turbo-prop engines, as well as other types of engines utilized for the main propulsion power of aircraft.

This application is a true division of my copending application, Serial No. 608,555, filed September 7, 1956, now Patent No. 3,002,346, entitled Fuel Control for Turbine Driven Compressor Unit," which in turn is a division of application Serial No. 209,929, filed February 8, 1951, now Patent No. 2,763,985 and entitled Fuel Control for Turbine Driven Compressor Unit.

One object of the herein-described invention is to provide reliable apparatus for the required purpose, which is 'of low weight and bulk, and wherein the various components are assembled so as to form an easily installed and easily removable packaged power unit, containing the required essential auxiliaries and controls for its operation. a

It is a further object to provide an airborne air supply unit which is especially adapted to furnish to a pneumatic starter, and wherein a novel dual bleed system is utilized for controlling the temperature of supplied air over a wide range of ambient temperature conditions, thus permitting attainment of aerodynamically matched conditions between the air supply unit and engine starter without the use of waste energy controls.

A further object is to provide a packaged power unlt in which a gas turbine is utilized for driving a compressor which furnishes the combustion air for the turbine, and in which distributed air for power purposes is bled'from the compressor outlet and proportionally mixed with hot turbine gases bled from the turbine inlet in such amounts as to control the bleed air energy level according to a predetermined schedule. I

Another object is to provide a novel governor control arrangement in connection with a fluid supply unit of the character described herein,'which modulates a fuel supply valve and is 'operatively associated with acceleration and high turbine exhaust temperature controls which are so 9 arranged as to modify the normal fuel valve operation.

Still another object is to provide in connection with such a unit novel means for unloading the unit during starting and idling periods, and for limiting the load which may be carried thereby so as to retain the operating characteristics within predetermined values.

It is also an object to provide novel automatic starting control for the fluid supply unit of the present invention, making use of novel electric switching means arranged to be energized from compressor outlet pressure, and having circuit controlling contacts which are sequentially operable at low pressure, high pressure, and very high pressure.

Briefly, the packaged power unit of the present invention comprises a hot gas turbine which is axially 3,133,414 Patented May 19, 1964 6 I CC aligned with and closely coupled to a compressor, with an intermediate accessory housing, the entire assemblage being mounted in an enclosing casing. The outlet of the compressor is connected with a suitable combustion chamber leading to the turbine inlet, and an air supply duct connects with the turbine inlet and compressor outlet through bleed connections which permit the dual bleeding of compressor air and hot turbine gases which by suitable apportioning control permit the delivery of the mixed fluid to the point of use at a desired energy level determined by the differential temperature between the ambient inlet air to the compressor and the temperature in the delivery duct.

The operation of the unit is normally regulated by a suitable governor, in this case a pneumatic control governor which is responsive to variations in ratio of compressor inlet and outlet pressures, the normal regulation of the governor in the control of fuel supply being augmented by acceleration control means during starting of the unit, and by turbine exhaust temperature responsive means during operation of the unit. Unloading and load limiting controls are provided for regulating the supply of fluid delivered to the point of use, and consequently the operating characteristics of the unit. The electrical control is arranged forswitch button start and stop from a remote control station, the control being timed in accordance with the starting acceleration of the unit through the use of a pressure responsive switching device having sequentially operable contacts arranged to function at low pressure, high pressure, and very high pressure. Safety controls are also provided for overspeed.

Further objects of invention will be brought out in the following part of the specification, wherein detailed description is forthe purpose of fully disclosing the invention without placing limitations thereon. 7

Referring to the accompanying drawings, which are for illustrative purposes only:

FIG. 1 is an isometric view of a packaged power unit embodyingthe features of the present invention, looking at the compressor inlet end, portions of the casing and component parts being cut away to disclose structural parts thereof; 7

FIG. 2 is likewise an isometric view, looking at the turbine exhaust end, portions of the casing being cut away to disclose interior parts of the unit;

FIG. 3 is a view schematically representing the component parts of the unit, together with the controls therefor; v

FIG. 4 is a view diagrammatically illustrating a pneumatic governor as utilized in connection with the controls, described herein; and V FIGS. 5, 6 and 7, respectively, diagrammatically illustrate thermally controlled valves as utilized in the present invention.

The Packaged Unit in General Referring generally to FIGS. 1 and 2 of the drawings, the packaged power unit of the present invention is illustrated as having its component parts compactly assembled within 'anenclosing casing as generally indicated at 19, which terminates in end walls 11 and 12, respectively, and in which the necessary connections are mounted to permit the unit to be quickly and easily installed or removed. a

Within the casing an air compressor 13 is interconnected with an axially aligned hot gas turbine 14, a housing 15 for associated accessories being interposed between the compressor and turbine.

Ambient air is admitted to the compressor through a tubular inlet 16 which is mounted in the end Wall 11 of the casing. Compressed air is conducted from the compressor through an outlet connection "17 to the inlet of a -13 combustion chamber 18 of the straight through type, the outlet end of this combustion chamber connecting with the turbine inlet. Exhaust from the turbine is through an outlet 19 mounted in the end wall 12 of the casing.

Combustion air in the combustion chamber is admitted through a perforated flame tube 2.) and mixed with a suitable fuel conducted into the combustion chamber through a supply conduit 21 and fixed area fuel nozzle 22. The fuel mixture is initially ignited by means of a suitable spark plug which may be disconnected once the unit has been properly started.

A distribution duct 24, for supplying compressed air to a point of use, is brought out through a tubular connection in the end wall 12 of the casing. The compressed air supplied through the duct 24 is a mixture of bleed air taken from the compressor and combustion chamber discharges. The hot gases are supplied through a bleed connection 25 of fixed area,'while the relatively cooler air from the compressor is supplied through a bleed connection 26, so that a by-pass in effect is formed around the combustion chamber 18. The temperature of air delivered to the distribution duct 24 is controlled by means of a modulating valve 27 which is mounted in the bleed connection 26. The actuating mechanism 27a of this valve is pneumatically controlled, air pressure acting to open the valve and a spring acting to bias the valve towards closed position. Between the modulating valve 27 and the inlet end of bleed connection 26, the bleed connection is provided with a branch conduit 28 which is connected with atmosphere and controlled bymeans of an unloading valve 29 arranged to be opened by the air pressure in the conduit 28, and actuated to closed position by the application of air pressure in its control mechanism.

Within the auxiliary housing 15, provision is made for mechanically driving a fuel pump 30, oil pump 31 and scavenger oil pump 32 through suitable transmission gearing 33 by the turbine of the unit, oil being supplied through a closed system from an oil tank 34 having an exteriorly accessible filler connection 35 at the turbine exhaust end of the casing Ill. The unit is arranged to be initially started and brought up to openating speed by means of a starting motor 36 forming a part of the electrical starting and control system which will hereinafter be described in detail.

Fuel and Oil Systems As schematically illustrated in FIG. 3, the fuel system is a simple single flow line in which a supply conduit 37 connects with the. inlet of the fuel pump 30, and an outlet connection 38 connects .with the fuel supply conduit 21 of the combustion chamber. A filter 39 in the fuel pump discharge connection protects the fuel system of the unilt, and a solenoid actuated shut-off valve 40, controlled as a part of the electric starting and control system to be hereinafter described, controls the fuel flow when starting and stopping the unit.

Fuel metering and control is accomplished by a by-pass valve 41 in a by-pass connection 42around the pump. The by-pass valve is arranged to be opened by fuel pressure from the discharge side of the fuel pump, and closed by air pressure under the control of a pneumatic governor 43 which is mounted in the air intake to the compressor 13. against abnormally high pressure by providing a pump by-pass connection 44 which is independentlycontrolled by a relief valve 45. By-passed fuel in both by-pass 42 and by-pass 44 will be returned to the pump inlet.

The oil system is a positive pressure circulating oil system in which the oil supply is contained within the oil tank 34. Oil is pumped by oil pump 31 from the oil tank and delivered under pressure to the unit, and is returned to the tank by means of the scavenger oil pump 32, an oil filter 46 being placed in the return line. As a safety measure, a connection 47 is provided between the As a safety measure, the fuel system is protected Electrical Starting and Control System Provision is made for carrying out the automatic starting and ignition, and the various steps are properly coordinated and sequentially effected upon the closing of a starting switch 49 having normally open contacts 50a and 501). This switch as well as a stop switch 51 having normally closed contacts 52 may be mounted at a remote station such as the pilots or flight engineers station and may also include indicating lamps, as illustrated at 53, as necessary.

The starting motor 36 is controlled through a starting relay 54- having an actuating coil 55 and normally open contacts 56a and 56b. An interlocking and overspeed relay 56 contains normally open contacts 57 and an actuating coil 58, one side of this coil being connected by a conductor 59 through normally closed contacts 66 of an overspeed switch 61. The relay 56 may be housed within a control box 62, as shown in FIG. 1, supported upon the intermediate auxiliary housing 15. Positioned adjacent the control box 62 is a pneumatically operated switch 63 which is connected through a conduit 64 to the compressor outlet so as to sense the compressor outlet pressure. This switch is arranged so as to sequentially close low pressure contacts, high pressure contacts, and very high pressure contacts. The low pressure contacts comprise normally open contacts 64a and normally closed contacts 64b. The high pressure contacts comprise normally closed contacts 65a and 65b, whereas the very high pressure comprises normally open contacts 66.

The operation of the electrical starting and control system will now be described. A suitable source of electric control current is provided, and may be from a suitable battery or generator, the source in the present instance being indicated by the numeral 67 with one side grounded.

In order to start the unit, it is only necessary to depress the starting switch 49 so as to close its contacts. The starting motor 36 will now be energized by activation of the starting relay 54 through the following circuit: from one side of the electrical source 67 through contacts 501;, conductor 68, closed contacts 64b, conductor 69, contacts 52 of the stop switch, through conductor 70, contacts 50a, through conductor 71 to one side of coil 55, and from the other side of this coil to ground. Energization of relay 54 causes it to close its contacts 56a and 56b. Closing of contacts 56a connects the starting motor 36 directly to the electrical source.

The relay 56, having one side of its actuating coil 58 connected through conductor 72 with the energized conductor 69, will be energized, since the other side of its coil is connected through conductor 59 and contact 69 of theoverspeed switch to ground or the other side of the circuit. Relay 56 now closes its contacts 57 which enables release of the starting switch by establishing a holding circuit on the starting relay as follows: from one side of the electrical circuit 67 through contacts 57, conductor 73, the closed contact 65a of the pneumatic switch, conductor 74, contacts 56b, and thence by conductor 71 through the coil 55 and to the other side of the electrical circuit.

The starting motor 36 will now continue to accelerate the unit, and when the rotating speed becomes sufi'iciently high to produce the necessary pressure in the combustion chamber for ignition, the. low pressure contacts of the pneumatic switch 63 will'be actuated from their normal positions so as to contacts 64a and open contacts 64b whereby to energize the solenoid shut-01f valve 46 to supply fuel to the combustion chamber, and energize the spark plug 23 for igniting this fuel. The solenoid shut-oif valve is energized through the following circuit: from the-high side of the electrical source 67, through conductor 75, contacts 57, conductor 73, contacts 52, conductor 69, the now closed contacts 64a, conductor 76 and conductor 77 to one side of the solenoid Valve 40, and from the other side of thisvalve to the grounded side of the electrical source. The spark plug is energized through a branch connection of conductor 76 which passes through normally closed contacts 65bof the pneumatic switch 63, thence through conductor 78 to an ignition coil 79 having a grounded connection.

After the unit has accelerated to sufiicient speed to support itself, the pneumatic switch 63 opens its high pressure contacts 65a and 6512 which open the holding circuit of the starting relay 54 to disconnect the starting motor, and disconnects the ignition coil 79 which energizes the spark plug. The unit then accelerates to an operating condition at which the governor control takes over, as will hereinafter be explained in detail.

In the event that compressor outlet pressure should reach a predetermined value of very high pressure, provision is made for indicating this condition to the remote control station. Such pressure will cause the pneumatic switch 63 to close its contacts 66, which will connect a branch of conductor 7 6 to conductor 80 which is connected to one side of signal lamp 53, the other side of this lamp being carried to the grounded side of an electrical source.

It Will be observed that during normal operation the energizing circuit of the solenoid shut-off valve 40 is through the contacts 57 of relay 56. Should an overspeed occur, which will open contacts 60, the energizing circuit r to the coil 58 will be interrupted and permit this relay to open its contacts and enable closure of shut-oil valve 40 to stop the unit. The unit may also be stopped by actuation of stop switch 51 which will open its contacts and also interrupt the energizing circuit of the coil 58 of relay 56, whereupon the relay will open its contacts to shut down the unit in the same manner as just explained.

Pneumatic Control System In its broad concept, the present invention contemplates that various types of governors may be utilized for normally controlling the unit of the present invention, such as a mechanical inertia type of governor, a hydraulically actuated governor and pneumatically controlled governor. For purposes of illustration and discussion, a pneumatic governor is utilized in connection with the pneumatic control system. This governor, as will be noted in FIGf3, is mounted at the inlet of the compressor 13 and is connected through a conduit 81 and filter 82 with conduit 64 which senses the compressor outlet pressure. This governor, as diagrammatically shown in FIG. 4, is arranged to modulate the supply of air pressure to conduit 83, the conduit 83 being connected through a branch connection 84- with the air pressure side of the by-pass valve 41 control. Air flow from conduit 81 to conduit 83 is controlled by a valve 81a operatively connected to a movable wall or diaphragm 82a subject on one side to compressor outlet pressure and on the otherside to compressor inletor atmospheric pressure, so that fuel supply will be varied directly in response to variations in the compressor inlet pressure. For example, if the compressor inlet air pressure decreases, the fuel supply will likewise be decreased. The governor 4-3 is thus basically arranged to control the .unit to a constant compressor pressure ratio over the load range thereon. Thus, by varying the. air pressure acting on the by-pass valve 41, the fuel supply to the cornbustion chamber is properly controlled. p

A metering orifice 85 bleeds fluid fromthe conduit '83 to the atmosphere at a restricted rate and thus permits the pressure in the conduit to be reduced aftervalve41 has been closed. .When'the pressure in conduit 83is reduced,

fuel pressure from pump 30 Will open valve 41 to by-pass fuel 1 V c 7 Provision is made for modifying the normal governor is provided a pressure vent valve 86 having a temperature sensing control element. This valve is connected by branch conduit 87 with conduit 83 so that at high temperature the pressure in line 83 will be reduced so as to permit greater by-pass of fuel through by-pass valve 41, whereupon the fuel furnished the combustion chamber will be reduced and the exhaust gas temperature lowered. As'dia'grammatically shown in FIG. 5, the vent valve 86 briefly comprises a housing having a tubular portion 86a within which there is mounted a rod 87a, these parts coacting to provide temperature responsive means in a manner well known in the art. Spring mounted Valves 88a and 88b, carried by the rod are operatively associated with valve seats 89a and 8% connected, respectively, with conduits 87 and 100. The arrangement is such that as the temperature of the tubular portion and rod increases, the valves will be moved toward open position. The valve housing is ventedto atmosphere at 90a.

It will be appreciated that there will be some time lag in the operation of'the vent valve 86. During starting of the unit, prior to the time when the governor control takes over, the fuel pump tends to furnish a greater amount of fuel than required. In order to reduce the fuelsupply during acceleration of the unit, an acceleration control valve 88 is provided for normally bleeding air from conduit 83 through a restricted orifice 89 and atmospheric vent 90, which reduces the pressure acting on the-valve 41a'nd permits by-pass of fuel and thus reduction of fuel supply to the combustion chamber. The

acceleration control valve is arranged to be closed by air pressure which is supplied through a conduit 91. During normal starting operation'and when the unit is idling, there is insufficient pressure acting to close the acceleration valve.

Pneumatic control air under pressure is also supplied from the compressor outlet through a conduit 92 and through a normally closed solenoid operated cut-off valve 93 to a distribution control pressure conduit 94 which may lead to a remote pneumatic control station, in this instance, a control station for an engine starter 95 connected to receive operating air from the distribution conduit 24. The cut-off valve 93 may therefore be utilized to initiate supply of air to a remote point of use, and as a consequence the loading of the unit. The conduit 94, it will be observed, is connected to the pressure closing side of the unloading valve 29, so that upon initiating control. which will result in loading of theunit, the unloading 'valve will be closed to shut off 'fiow through the conduit 28. Sincethe conduit 91 is also connected to distribution conduit .94, the placing of pressure on conduit94 will also result in closing the acceleration control valve 88.

w A load limiting valve 96 is mounted in the distribution duct 24. In practice, this valve, as well as a thermally controlled valve. 97, is preferably connected to the endof the duct 24, which is shown in FIG. 2 as projecting lfrom'the casing end wall 12, in order'to prevent time lag in operation; The valve 96 is operated by an control upon the'occurrence of predetermined over-ternperature in the turbine exhaust. For such purpose'there va predetermined schedule;-

valve closing direction and bypressure from conduit 98 in a valve'opening direction, the conduit 98 being connected to conduit 92 through a metering orifice 99 which limits the-pressure supply from the conduit 92 and permits actuation of the load limiting valve by bleeding oif air from conduit 98 through connection conduit 100 at a predetermined temperature setting of pressure vent valve 86. I I

Since the power available from expansion of compressed a ir supplied from the unit 'varies directly as the temperature of the source, it is contemplated in the present invention to control .the. temperature according to I k The bleed air temperature furnished through the ,duct 24 is controlled to a constant increase above ambient by mixing combustion gases with the compressor discharge bleed-air." The mixing of bleed air and hot gases is accomplished through the operation of the modulating valve 27 which is operatively arranged to be spring closed and pneumatically opened. Pressure for actuating the valve 27 is controlled through a thermally controlled valve 101 located in the compressor inlet at the end of a conduit 102, this valve being arranged to vent the conduit to atmosphere in response to temperature changes in ambient air entering the compressor. Operating air pressure is normally supplied to the conduit 102 from conduit 94 which is connected through conduit 103 and the thermally controlled valve 97 to the conduit 102. A branch conduit 104 connects conduit 102 with the actuating mechanism of valve 27. The valves 97 and 101 are both arranged to open when the associated temperature increases and are, ingeneral, of similar construction to that of valve 86, previously described. As diagrammatically shown in FIG. 6, the valve 97 is, in this case, not vented to atmosphere and contains only the valve 88a, the seat 89a is, in this case, connected to conduit 103. On the other hand, valve 101, as shown in FIG. 7, is vented to atmosphere and the valve seat 89a is, in this case, connected to conduit 102, the valve seat 8% and its conduit connection being eliminated. With the arrangement just described, it will be apparent that if the temperature at the valve 97 increases too high, this valve opens and increases the pressure acting in the conduit 104, thus actuating valve 27 toward open position, so as to supply a greater amount of compressor outlet air through the bleed connection 26 for restoring the temperature to normal. A decrease in temperature at the valve 97 acts conversely to close the valve 27 and cause the temperature to be increased toward normal condition.

At the intake of the compressor, the valve 101, upon increased ambient temperature, will open so as to vent the conduit 102 and thus decrease the pressure acting upon the operating mechanism of valve 27, thus enabling this valve to move toward closed position under its spring action. This will decrease the flow of relatively cooler airthrough the bleed connection 26 and enable the hot turbine gases from bleed connection 25 toraise the temperature at valve 97 so as to restore the proper pressure differential between the temperature at valve 97 and the ambient air temperature at valve 101. -With a decrease of ambient temperature at valve 101, the operation will be just the opposite.

It will therefore be apparent that by controlling the modulating valve 27 in the manner described above, a scheduled temperature differential may be maintained between the temperature of delivered air through the duct 24 and the temperature of ambient air entering the compressor 13. In the case of the utilization of the hereindescribed unit to supply operating air pressure to an engine starting turbine 95, this arrangement permits aerodynamically matched operation of the turbine compressorunit and the air starter through a wide range of ambient temperatures without the use of waste energy controls.

It will also be appreciated that a power packaged unit of the herein-described construction may be utilized to selectively furnish through proper selective valves operative air pressure to a plurality of starting turbines.

It is appreciated that various modifications may suggest themselves to those skilled in the art without departing from the spirit of the present invention, and hence, it is desired that the invention shall not be restricted to the specific form shown or'uses mentioned, except to the extent indicated in the appended claims.

I claim:

1. Air supply apparatus, comprising: a gas turbine having a combustion chamber; a compressor driven by said turbine having an outlet connected to said combustion chamber; a fuel supply connection to said chamber; a fuel control valve in said supply connection; an electric fuel igniter operatively associated with .saidchamber; a

5'5 starter motor for said turbine; pressure responsive switching means controlled by the compressor outlet pressure, said means having sequentially operable low pressure contacts, high pressure contacts, and very high pressure contacts; means including lower pressure contacts in circuit with a starting switch operable to energize said starter motor; circuits established by actuation of the lower pressure contacts for energizing said fuel control valve and said fuel igniter, the circuits through high pressure contacts being operable at high pressure to disconnect said fuel igniter and said starter motor; an overspeed relay circuit having a switch responsive to predetermined excessive speed of said starter motor to interrupt current flow to said starter motor independently of the condition of said pressure responsiveswitching means; and a selectively operated switch means for opening said overspeed relay circuit to interrupt the operation of said starter motor at any desired time prior to the operation of said high pressure contacts and said speed responsive switch.

2. Air supply apparatus comprising: a gas turbine having a combustion chamber; a compressor driven by said turbine having an outlet connected to said combustion chamber; a fuel supply connection to said combustion chamber; an electrically actuated fuel control valve in said supply connection; an electric fuel igniter operatively associated with said chamber; a starter motor for said turbine; pressure responsive switching means controlled by the compressor outlet pressure, said means having a plurality of switches, some being normally closed and others normally open; a starting relay for controlling in part said starter motor; an overspeed switch responsive to the speed of operation of said turbine; an overspeed relay controlled in part by said overspeed switch; a manually operated start switch; and circuit means connecting said switches, said control valve, said igniter, said starting motor, and said relays, the actuation of said starting switch energizing said relays to initiate and maintain the flow of current from a source thereof to said starting motor to rotate said turbine and compressor, a predetermined compressor output pressure closing a predetermined switch of said pressure responsive switching means to connect said fuel control valve and igniter with a current source, a predetermined additional compressor output pressure opening a predetermined switch of said pressure responsive switching means to disconnect said starter motor and igniter from the current source, said overspeed switch being operative at a predetermined turbine speed to de-energize said overspeed relay and disconnect said fuel control valve from the current source.

3. Air supply apparatus comprising: a gas turbine having a combustion chamber; a compressor driven by said turbine having an outlet connected to said combustion chamber; a fuel supply connection to said combustion chamber; an electrically actuated fuel control valve in said supply connection; an electric fuel igniter operatively associated with said chamber; a starter motor for said turbine; pressure responsive switching means controlled by the compressor outlet pressure, said means having a plurality of switches, some being normally closed and others normally open; a starting relay for controlling in part said starter motor; an overspeed switch responsive to the speed, of operation of said turbine; an overspeed relay controlled in part by said overspeed switch; a normally open start switch; circuit means connecting said switches, said control valve, said igniter, said starting motor and said relays, the closing of said starting switch energizing said starting and overspeed relays, the former serving to connect said starter motor with a current source and the latter cooperating with a normally closed switch of said pressure responsive switching means to establish a holding circuit for said starting relay, operation of said starter motor rotating said turbine and compressor, a predetermined compressor output pressure closing a predetermined switch of said pressure responsive switching means to connect said fuel control valve and igniter with a current source, a predetermined additional compressor output pressure opening predetermined switches of said pressure responsive switching means to disconnect said igniter from the current source and intermpt the holding circuit for said starting relay and thus disconnect said starter motor from its current source; and a normally closed stop switch, the opening of said stop switch serving to tie-energize said overspeed relay and disconnect said fuel valve from its current source.

4. Air supply apparatus comprising: a gas turbine having a combustion chamber; a compressor driven by said turbine having an outlet connected to said combustion chamber; a fuel supply connection to said combustion chamber; an electrically actuated fuel control valve in said supply connection; an electric fuel igniter operatively associated with said chamber; a starter motor for said turbine; pressure responsive switching means controlled by the compressor outlet pressure, said means having a plurality of switches, some being normally closed and others normally open; a starting relay for controlling in part said starter motor; an overspeed switch responsive to the speed of operation of said turbine; an overspeed relay controlled in part by said overspeed switch; a normally open start switch; circuit means connecting said switches, said control valve, said igniter, said starting motor, and said relays, the closing of said starting switch energizing said starting and overspeed relays, the former serving to connect said starter motor with a current source and the latter cooperating with a normally closed switch of said pressure responsive switching means to establish a holding circuit for said starting relay, operation of said starter motor rotating said turbine and compressor, a predetermined compressor output pressure closing a predetermined switch of said pressure responsive switching means to connect said fuel control valve and igniter with a current source, a predetermined additional compressor output pressure opening predetermined switches of said pressure responsive switching means to disconnect said igniter from the current source and interrupt the holding circuit for said starting relay and thus disconnect said starter motor from its current source; an electrically energized warning device, a second predetermined additional compressor output pressure closing another normally open switch of said pressure responsive switching means to connect said warning device with a current source; and a normally closed stop switch, the opening of said stop switch serving to de-energize said overspeed relay and disconnect said fuel Valve from its current source.

References Cited in the file of this patent UNITED STATES PATENTS 2,476,218 Prime July 12, 1949 2,699,218 Nims Jan. 11, 1955 2,741,086 Machlanski Apr. 10, 1956 2,832,193 Wood Apr. 29, 1958 

1. AIR SUPPLY APPARATUS, COMPRISING: A GAS TURBINE HAVING A COMBUSTION CHAMBER; A COMPRESSOR DRIVEN BY SAID TURBINE HAVING AN OUTLET CONNECTED TO SAID COMBUSTION CHAMBER; A FUEL SUPPLY CONNECTION TO SAID CHAMBER; A FUEL CONTROL VALVE IN SAID SUPPLY CONNECTION; AN ELECTRIC FUEL IGNITER OPERATIVELY ASSOCIATED WITH SAID CHAMBER; A STARTER MOTOR FOR SAID TURBINE; PRESSURE RESPONSIVE SWITCHING MEANS CONTROLLED BY THE COMPRESSOR OUTLET PRESSURE, SAID MEANS HAVING SEQUENTIALLY OPERABLE LOW PRESSURE CONTACTS, HIGH PRESSURE CONTACTS, AND VERY HIGH PRESSURE CONTACTS; MEANS INCLUDING LOWER PRESSURE CONTACTS IN CIRCUIT WITH A STARTING SWITCH OPERABLE TO ENERGIZE SAID STARTER MOTOR; CIRCUITS ESTABLISHED BY ACTUATION OF THE LOWER PRESSURE CONTACTS FOR ENERGIZING SAID FUEL CONTROL VALVE AND SAID FUEL IGNITER, THE CIRCUITS THROUGH HIGH PRESSURE CONTACTS BEING OPERABLE AT HIGH PRESSURE TO DISCONNECT SAID FUEL IGNITER AND SAID STARTER MOTOR; AN OVERSPEED RELAY CIRCUIT HAVING A SWITCH RESPONSIVE TO PREDETERMINED EXCESSIVE SPEED OF SAID STARTER MOTOR TO INTERRUPT CURRENT FLOW TO SAID STARTER MOTOR INDEPENDENTLY OF THE CONDITION OF SAID PRESSURE RESPONSIVE SWITCHING MEANS; AND A SELECTIVELY OPERATED SWITCH MEANS FOR OPENING SAID OVERSPEED RELAY CIRCUIT TO INTERRUPT THE OPERATION OF SAID STARTER MOTOR AT ANY DESIRED TIME PRIOR TO THE OPERATION OF SAID HIGH PRESSURE CONTACTS AND SAID SPEED RESPONSIVE SWITCH. 